Zhou Bo, Wei Fan-Yan, Kanai Narumi, Fujimura Atsushi, Kaitsuka Taku, Tomizawa Kazuhito
Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan.
Department of Molecular Physiology, Faculty of Life Sciences, Kumamoto University, Kumamoto 860-8556, Japan
Hum Mol Genet. 2014 Sep 1;23(17):4639-50. doi: 10.1093/hmg/ddu184. Epub 2014 Apr 23.
Single-nucleotide polymorphisms (SNPs) in CDKAL1 have been associated with the development of type 2 diabetes (T2D). CDKAL1 catalyzes 2-methylthio modification of adenosine at position 37 of tRNA(Lys)(UUU). A deficit of this modification causes aberrant protein synthesis, and is associated with impairment of insulin secretion in both mouse model and human. However, it is unknown whether the T2D-associated SNPs in CDKAL1 are associated with downregulation of CDKAL1 by regulating the gene expression. Here, we report a specific splicing variant of CDKAL1 termed CDKAL1-v1 that is markedly lower in individuals carrying risk SNPs of CDKAL1. Interestingly, CDKAL1-v1 is a non-coding transcript, which regulates the CDKAL1 level by competitive binding to a CDKAL1-targeting miRNA. By direct editing of the genome, we further show that the nucleotides around the SNP regions are critical for the alternative splicing of CDKAL1-v1. These findings reveal that the T2D-associated SNPs in CDKAL1 reduce CDKAL1-v1 levels by impairing splicing, which in turn increases miRNA-mediated suppression of CDKAL1. Our results suggest that CDKAL1-v1-mediated suppression of CDKAL1 might underlie the pathogenesis of T2D in individuals carrying the risk SNPs.
CDKAL1基因中的单核苷酸多态性（SNPs）与2型糖尿病（T2D）的发生有关。CDKAL1催化tRNA（Lys）（UUU）第37位腺苷的2-甲硫基修饰。这种修饰的缺陷会导致蛋白质合成异常，并且在小鼠模型和人类中均与胰岛素分泌受损有关。然而，尚不清楚CDKAL1中与T2D相关的SNPs是否通过调节基因表达与CDKAL1的下调有关。在此，我们报道了一种CDKAL1的特定剪接变体，称为CDKAL1-v1，在携带CDKAL1风险SNPs的个体中其水平明显较低。有趣的是，CDKAL1-v1是一种非编码转录本，它通过与靶向CDKAL1的miRNA竞争性结合来调节CDKAL1水平。通过对基因组的直接编辑，我们进一步表明SNP区域周围的核苷酸对于CDKAL1-v1的可变剪接至关重要。这些发现揭示，CDKAL1中与T2D相关的SNPs通过损害剪接降低了CDKAL1-v1水平，这反过来又增加了miRNA介导的对CDKAL1的抑制作用。我们的结果表明，CDKAL1-v1介导的对CDKAL1的抑制作用可能是携带风险SNPs个体中T2D发病机制的基础。
